This invention relates to the recovery of constituents from subterranean ore deposits and, more particularly, to an in-situ method of recovery that is particularly effective in the production of shale oil.
One known technique for recovering shale oil is to set up an in-situ retort in a subterranean oil shale deposit. The shale within a recovery zone is fragmented, the shale at the top of the recovery zone is ignited, and air is supplied to the top of the recovery zone to sustain combustion, which proceeds slowly down through the fragmented shale in the recovery zone. As burning proceeds, the heat of combustion is transferred to the shale below the burning front to release the shale oil and gases therefrom by a retorting process. Thus, a horizontal retorting front moves from top to bottom of the recovery zone in advance of the burning front, and the resultant shale oil and gases pass to the bottom of the recovery zone for collection.
It is important that the gas flow through the recovery zone is uniform. If the gas flow is uneven, i.e., more gas flows downward through certain paths than through other paths, the retorting front may become skewed. The carbonaceous values released in the lagging region of the retorting front may be oxidized in the leading region of the burning front, thereby reducing the yield of the process.